For people who are moving to Windows Phone 8 from iOS / Mac / iCloud, here's what I did to make my essential data sync cross-platform on all devices:

CONTACTS and CALENDARS

1. Sign up for Microsoft Hosted Exchange (around US$4 per month for their "Hosted Email" plan at the Office 365 website).
2. On your Mac, go to System Preferences > Mail, Contacts and Calendars. Add the Microsoft Exchange account and enable Contacts, Calendars and Reminders.
3. Go in to the Contacts app, where all your iCloud contacts are stored. Select all your contacts, then drag them in to "Contacts" under Exchange on the left. This effectively copies all your iCloud contacts in to your Exchange account. Close Contacts.
4. Go in to Calendar, click on "Calendars" to bring up the list of all your calendars. Highlight each individual calendar and choose File > Export > Export. Export the calendar temporarily to your desktop. Repeat this for each of your calendars listed.
5. Go to System Preferences > Mail, Contacts and Calendars. Choose "iCloud" and uncheck "Calendars" and "Contacts and Reminders". This removes the iCloud data from your Mac.
6. Go back in to Calendars and you will see Exchange listed in the Calendars list but no calendars present. One-by-one, choose File > Import and import each calendar from the desktop which you just exported from iCloud.

Now you have copied all your contacts and calendars from iCloud to Exchange and are primarily using Exchange to store and synchronise this data now on your Mac.

7. Go to your Windows Phone and under Settings > email+accounts, choose "add an account" and set up your new Exchange account there. Under "content to sync", make sure you choose "Contacts" and "Calendar". Your contacts and calendars will then sync to your Windows phone.
8. Go in to any i-devices you have (iPhone, iPad, iPod Touch), go to Settings > Mail, Contacts and Calendars, choose your iCloud account and turn OFF Contacts and Calendars. Then add your Exchange account and turn ON Contacts and Calendars. Again, everything will then sync up to your i-devices.

By following the above steps, you can sync your Contacts and Calendars across your Mac, i-Devices AND your Windows Phone 8 device seamlessly.

TASK MANAGEMENT

I previously used "Things" for Mac and iOS to manage tasks and projects. I've been looking for a good cross-platform alternative, as there is no "Things" for Windows Phone 8. After trying many solutions, I've settled on getitdoneapp.com. It costs a US$35 per year subscription to use, but they have Windows Phone 8 and iOS apps in the respective WP8 and iOS app stores. On the desktop (Mac or PC), you access your tasks in a web browser. HOWEVER, you can create a kind of desktop app version of this on the Mac by using something called "Fluid" (fluidapp.com).

I realise that all this costs some money in terms of new subscriptions, and you may not be willing / able to justify this extra cost. However, for me, this means I can now carry and sync all my important data with me between my Mac, iOS devices and my beautiful new Windows Phone. Sweet!

I agree that OneNote is a good choice too, especially as it's free and also available on iOS and on the Mac through it's WebApp (which can also run as a "Fluid" app as mentioned in my post above).

I tried using OneNote but didn't take to it myself because I like to have a list of tasks with checkboxes which I can drag-and-drop order easily and then, when I complete a task, check the box and the task automatically disappears.

With OneNote, you can have checkboxes, but checking them doesn't make the task disappear, you still have to manually do that. Also, to rearrange tasks, you have to delete and re-paste as in any standard document. So, I personally prefer a dedicated task manager that adds the little touches I'm used to.

I was hoping that Wunderlist would fit the bill, they had a Windows Phone 7.x client as well as running on iOS and Mac but have recently declared that they will not be developing a Windows Phone 8 client - boo! Anyway, getitdoneapp is working well for me on all platforms so far.

Will this sync all icloud calendars? For instance I can sync my icloud calendars (wifes, mine, daughters) to Outlook 2013 but can only sync whichever account is default primary to my WP8. For instance:myname@icloud.com ---> apple id
-RobR --> a calendar
-Nilla --> a calendar

The icloud app properly syncs those to my physical Outlook 2013 program. But WP8 of course completely ignores that choosing to only sync with Outlook.com so I made a new alias and made it primary - mynewalias@outlook.com then I added it to Outlook2013 and to my Ipad which lets me then simply make any calendar entries and they simultaneously update: iPad, WP8, and Outlook2013.
HOWEVER I still can't get my wife's iPhone calendar (Nilla) to sync to my WP8. We NEED access to each other's calendars.

I think she may have to post her calendar information to the same calendar file "mynewalias@outlook.com" instead of the Nilla one.